What are Space Slugs?

Escaping Imperial fighters, Han Solo flies his Millenium Falcon into a cave- before the famous words “This is no cave.” are uttered. They were, in fact, in the belly of a Space Slug.

Worm-like creatures growing as large as 900 meters, space slugs inhabit deep caverns on larger asteroids near the planet Hoth. It has long been rumored that a space pirate planted the huge slugs as guardians for his hidden treasure and bases.
The slugs are hardy, existing on virtually no atmosphere. Silicon-based life-forms, they live for long periods by breaking down rock and subsisting on mineral content.

Space slugs are plagued by parasites known as mynocks, which they sometimes feed on. Space slug flesh has a number of commercial uses. The creatures reproduce through fission, splitting into two separate beings.